Silencer unit



April 1946- 1 H. L. MAGlLL 2,397,556

SILENCER UNIT Filed March 2, 1944 2 Sheets-Sheet 1 I NVENTOR HerfierfL.Ma gill BY April 2', 1946. H. L. MAGILL SILENCER UNIT 2 Sheets-Sheet 2Filed March 2, 1944 W w L A r.

ER qQm w Patented Apr. 2, 1946 UNITED STATES PATENT OFFICE SILENCER UNITHerbert L. Magill, Chicago, Ill.

Application March 2, 1944, Serial No. 524,742

14 Claims.

This invention relates to mufflers or silencer devices for reducing theforce or intensity of sound incident to the discharge of gases throughrestricted passages under high pressure.

One of the important objects of the invention is the provision of a newand improved silencer for reducing the intensity of sound incident tothe exhaust discharge of internal combustion engines.

Another object of the invention is the provision of a new and improvedsilencer for materially reducing the intensity of sound discharge of anygas under high pressure into the atmosphere without creating additionalback pressure on the apparatus discharging the gas.

Another object of the invention is to so discharge portions of thexhaust gas laterally that in combination with the natural air streamflow around the exterior of the exhaust silencer when in motion at highspeeds, a suction effect will be produced to react on the dischargeexhaust flow from the engine to facilitate and improve the scavenging ofthe engines cylinders and thereby tend to increase the power output ofthe enme. g Another object of the invention is to provide a device thatwill cool exhaust gases by expansion prior to release of the gases tothe atmosphere, not only to avoid overheating of the device itself butalso to prevent discharge into the atmosphere of flame, sparks andhighly heated particles.

A further object of the invention is to provide a form of constructionfor the exhaust silencer that will create a minimum of aerodynamicresistance when in motion through the atmosphere, and when not in motionthe lateral and rearward discharge of the exhaust gases through theanterior passages, and flowing rearwardly over the following passages,will tend to reduce pressur in those passages by entrainment of thegases therein, whereby even though the unit be not moving the enginesefiiciency will be increased by reducing the back pressure of theexhaust.

A still further object of the invention is the provision of a new andimproved silencer that is simple in construction, inexpensive tomanufacture, easily assembled, that is efficient in operation, and thatmay be easily and readily applied to any exhaust discharge mechanism.

Other and further objects and advantages of the invention will besuggested from the following description, taken in connection with theaccompanying drawings, in which Fig. 1 is a rear elevation of thesilencer device embodying one form of the invention;

Fig. 2 is a vertical section on the line 22 of Fig. 1;

Fig. 3 Fig. 2;

Fig. 4 is a rear elevation of a modified form of construction;

Fig. 5, is a section on the line 5-5 of Fig. 4;

Fig. 6 is a section on the broken line 65 of Fig. 5;

Fig. 7 is a section on the line 1-1 of Fig. 6; and

Fig. 3 is a perspective view of the casing shown in Fig. 5, on a reducedscale.

While the silencer unit is adapted to be used invarious relations, andon numerous constructions where it is desirable to eliminate noiseincident to the escape of gas under high pressure and velocity, asexhaust from engines, discharge from gunsand other firearms and thelike, the embodiments selected to illustrate the invention relate moreparticularly to silencers for internal combustion engines for use inmotor vehicles, as airplanes, land vehicles, and the like.

Referring now to the drawings, th reference character I!) designates thesilencer unit, which comprises a plurality or pack of transvers platesor wall members I! in the form of hollow truncated cones coaxiallyarranged and nested in spaced relation, with their small ends or inneredges all turned in the same general upstream direction. The directionfrom whence comes the exhaust gases, or gases under pressure, will, forconvenience of description, be termed the forward end of the device,which in Fig. 2 is at the left of the drawings.

The front end of the silencer unit is provided with suitable means forattaching the unit to an exhaust pipe or the like. Any appropriate meansmay be employed for this purpose, depending on the nature of the exhaustconstruction. As shown by way of example, a. tubular attaching member i2is employed for this purpose. It is adapted to slide or telescope overthe rear end of the exhaust pipe 13 of the engine. Any convenient meanssuch as the clamp i4, comprising a strap extending around the ex-- haustpipe l3 and clamped by the bolt I5, may be employed for holding thesilencer positioned on the exhaust pipe, the tubular member l2 beingslotted at its end, as at 42 to permit contraction for this purpose.

A curved conical head cap or front cap member i6 is provided forreinforcing the forward end portion of the silencer unit, and forinsuring a is a section on the broken line 33 of finished appearance tothe unit. The forward end of the head cap tapers to a sleeve-likeportion 11, which telescopes over the tubular attaching member l2adjacent the forward end of the latter and is rigidly attached thereto,as by spot or seam welding, or the like, The rear end of the cap memberit is flared outwardly, as at [8, and is rigidly attached to theforemost plate H, which in turn has its outer edge extending rearwardlyand rigidly secured in the rear end of the cap member, as by welding orthe like, as shown at 2|. The forward end of the foremost plate l9telescopes over the tubular attaching member l2, as at 22, and isrigidly secured thereto.

The rear end of the silencer unit is provided with a rear or tail capmember 23, which comprises a tubular cone-like forwardly extendingportion Z l and a return bent portion 25 telescoped within a rearwardlyextending flange 26 on the rearmost conical plate or gas divertingmember El of the exhaust unit I I. The forward end portion of theconical plate or gas diverting member 21 extends rearwardly to form anannular projection 28 that telescopes within the end of the forwardlyextending portion 24 of the cap member 23, and is clamped in position,as will presently appear.

Suitable means are provided in the unit between the front and rear capmembers for diverting portions of the exhaust from the main stream,expanding each portion separately and discharging the same from thesides of the unit into the atmosphere, whereby the noise and backpressure incident to the exhaust of the conventional internal combustionengine will be reduced to a minimum.

In the construction selected to illustrate one embodiment of theinvention, the mechanism disclosed comprises means at intervals alongthe unit that successively diverts outer annular'portions of the mainexhaust stream outwardly and other means for radially expanding the samein such manner that the diverted portions discharge at the sides of theunit, mingling with the atmosphere at pressure and densitiesapproximating that of the atmosphere,

In the form of construction shown in Figs. 1, 2 and 3, there is provideda plurality of gas or exhaust diverting members or plates 3|, 32, 33 andEl, which form what will be termed gas expansion chambers so, 31b, 36and 3e, between adjacent gas diverting members, respectively. Thus gasexpansion chamber 30 lies forward of member 3!, chamber 35% extendsbetween members ti and 32, chamber 30 is bounded by members 32 and 33,and chamber 33 extends rearward from member 30 to member 21. These gasdiverting members, which may be regarded as orifice means, are each moreor less conical, are hollow, and are shaped like the frustrums of hollowcones with the smaller ends turned forwardly and coaxially arranged.These gas diverting members have gradually decreasing openings orinternal diameters, from the front to rear of the silencer unit, attheir forward ends, and allhave the same external diameters at theirrearor outer edges. Thus the successive entrances to the expansion chambersare progressively restricted. The rear or outer edges of these exhaustdiverting plates or members are curved rearwardly or downstream, asshown at 34 in Fig. 2, for directing the exhaust gases rearwardly attheir peripheral edges.

Appropriate means within the gas expanding chambersare'provided forassisting in expanding the annular streams of exhaust gases that arediverted from the main stream. As shown, an assembly of exhaustexpanding members are employed between the foremost plate 19 and theforward exhaust diverting member 3i, and between each two adjacentexhaust diverting members 3t, 32, 33 and 2i. Any suitable number ofthese diverting members may be employed. The gas expanding members ofeach assembly are substantially like those in the remaining -expandingchambers, and each comprises the transverse plates or wall members 36,31, 38, 39, 41] and ii. There are two sets of these plates or gasexpanding members, all of which are shaped like hollow frustrums ofcones of the same internal diameters at their inner or foremost ends.The internal diameters of these smaller ends are substantially the sameas that of the attaching sleeve member l2.

The plate members having the odd reference numerals are of substantiallythe same form'and dimension, and are shorter and of less diameter attheir outer or rear edges than the remaining ones. In other words, theplate members 35, 31, 39 and 4! are shorter and are of less diameter attheir outer ends than the even numbered plate members 36, 38 and 49. Theplate members of the first-mentioned set have their outer peripheraledges substantially straight and extending outwardly and rearwardly. Theremaining plate members of each assembly are of the same outer diameteras the exhaust diverting members 3|, 32, 33 and 2?, and are also curvedrearwardly like those members, and terminate outwardly of the outerstraight edges of the plate 35, 31, 39 and M, for directing the exhaustrearwardly over those plates. In other words, some of the transverseplates have outer edges extending beyond the outer edges of adjacentplates downstream therefrom and turned toward said adjacent plates. Thusthe transverse plates define lateral escape passages for the exhaustgas, and some of the passages direct their discharge across saidadjacent passage exits to promote exhaust from the adjacent passages.

The exhaust diverting plate members and the exhaust expanding platemembers have similar contours, and are held in assembled or spacednested relation by a plurality of support means in the form of bolts orrods .42, which extend through openings in radially extending portions43 formed in each of these plate members. Any suitable number of theserods may be employed, three being shown spaced apart. The plate membersare held in spaced relation by spacer blocks 44 between each twoadjacent discs, and at the ends of the silencer unit betwen the endplates and the head and tail caps, respectively. Suitable nuts 45 and 46on the ends of the bolts 42 clamp the parts in assembled relation toform a unitary structure.- The nuts 45 are preferably welded to theplate 3 in order to facilitate assembly. The nuts it for the rear endsof the bolts AZmay be extended and internally threaded for receivingbolts ill for clamping the rear cap member 23 in telescopic relation tothe flange 26 and rear extension 23 of the rear plate member 21.

It will thus be seen that the diverting plate members 3!, 32, 33 and 211will successively skim off or divert an annulus from the periphery ofthe rearwardly moving stream of exhaust gases and direct the same intothe expansion chambers 30, 30 33 and 35!, between the adjacent exhaustdiverting plate members; and it will be appreciated that this divertedgas is expanded as it flows radially outward and rearward between theexhaust expanding plate members. Each of these gas diverting andexpanding members has its inner end and intermediate portion curvedrearwardly, with the inner portion of the curve at a more acute angle tothe axis of the unit than the outer portions of the curve, so as to formpassages between the plate members that increase materially incross-sectional area from their inner to their outer ends or towardtheir outer peripheries.

In the operation of the device the exhaust gases passing rearward intothe silencer unit will have an annular peripheral portion of the streamof exhaust gases escaping from the pipe 13 diverted radially outwardlyinto the expansion chamber 30, between the plate member 3| and the frontplate member 19. When the exhaust passes beyond the tubular member !2,the entire stream expands to a certain extent because the peripheralportion of it expands into the expansion chamber immediately after itleaves the tubular member [2, and before it reaches the first divertingplate 3!. The gas diverted by the plate 3| and divided by the gasexpanding members into a plurality of thin streams moving at highvelocity, will not only be expanded radially but will be materiallyincreased in volume due to the increasing cross-sectional area of thepassages toward the outer periphery of the silencer unit, and willtherefore be first cooled and then discharged at comparatively lowvelocity and with very little noise, if any at all. This is consideredan important feature of the invention.

The remaining main stream of exhaust gas, now slightly expanded butreduced in diameter by the initial skimming action of the exhaustdiverting member 3!, as indicated by the space between the dot and dashlines (1-1) and cd, Fig. 2, flows rearwardly and will further expand inthe chamber 30 and have another annulus of the stream diverted orremoved by the plate member 32, thus further reducing the stream inpressure and also in diameter, as indicated by the space between the dotand dash lines e and gh, Fig. 2.

This annulus of exhaust is diverted into the expansion chamber 3!]formed between the exhaust diverting plates 3| and 32, and is furtherexpanded due to increase in radius and in crosssectional area of thepassages between the expanding plates in this last-named chamber.Likewise, the plate member 33 further reduces the diameter of theexhaust stream, as indicated by the dot and dash lines 2 -4 and lcl. Thestream is further reduced by the plate member 21, and this reducedstream expands radially within the cap member 23.

It will be noted that the successive expansion chambers offerprogressively less obstruction to the exhaust gases. In the first place,while the same number of expanding plates is employed in each of theexpansion chambers 30, 30 30 and 30, the successive chambers areprogressively increased in length with consequent increased spacingbetween the expanding plates. In the second place, the volume of the gasstream progressively lessens along the series of expansion chambers, sothat even if the expansion chambers were of uniform size the chamberswould be of increasing size relative to the volumes of gas admittedthereto. In the third place, the radial distance between the expandingplates and the gas stream entering the expansion chambers increases inthe successive chambers. Thus the space in the chambers 30, forinstance, between the inner peripheral edges of the expansion membersand the line z'7', is greater than the corresponding space in thepreceding chamber. As a result of this arrangement the pressure in themain stream is more and more reduced, with a corresponding reduction invelocity, before it enters the rear cap member 23, where it is furtherexpanded and discharged into the atmosphere at greatly reduced pressureand velocity.

The radial expansion of one annulus of the exhaust after another, andthe continued ex pansion of the main exhaust stream as it passes oneexpansion chamber after another, prevents noise and permits an almostfree expansion of the gas, whereby there is little or no back pressureon the engine, thereby adding to its efficiency.

In the form of construction described above, the silencer unit iscylindrical in shape and the exhaust is discharged from the entireperiphery of the cylinder. Under certain conditions it is desirable thatthe exhaust from the silencer unit be discharged from a portion of theperiphery of the silencer only. For instance, in the interest of safetyagainst fire and carbon monoxide gas escaping into the vehicle, in theuse of the silencer unit as a mufller for certain types of land motorvehicles, and for aircraft and the like, it is necessary, or at leastdesirable, that the exhaust gases be directed away from the vehicle bodyor away from adjacent combustible portions of the structures-on whichthe device is employed. All forms of my invention provide an exhaustchannel having at least one side open to the atmosphere, and the formabove described provides an exhaust channel open to the atmosphere onall sides. The channel in the form next described is open to theatmosphere on only one side.

In the form of construction shown in Figs. 4 to 8, the silencer is of aform in which the discharge diverting and expanding members are in theshape of curved substantially rectangular plates, and the portion of thecasing opposite these plates is more or less semi-circular, forming aconduit along which portions of the exhaust are discharged laterally. Inthis form of construction the silencer unit 5% is of a type in whichportions of the gases are discharged in one direction only, which may belaterally or down wardly, depending on how the device is attached. Thecasing 5i of the silencer unit 58 is channel form in cross-section,having the flanges 52, 53, extending laterally in spaced relation andhaving a curved web portion 54. The casing is split into two sections ina plane extending midway between the flanges 52, 53, and thecurved-edges are provided with outwardly extending flanges 55, 56,rigidly secured together by any suitable means. The curved portions ofthe two sections of the silencer unit form the main exhaust conduit 1 Ithat has its rear portion slightly inclined, or'at an angle, to theforward portion, as shown in Fig. 5, and as indicated at 51 in Fig. 4.

The two sections of the silencer unit are together provided with acylindrical sleeve portion 58, Fig. 8, which telescopes an attachingsleeve portion 59 and is rigidly attached thereto. The forward end ofthe casing 5|, Fig. 8, has the flanges 52, 53, bentinwardly toward eachother, as at 50 and 50 to form a curved Wall constituting the foremostexpanding plate IS. The adjacent edges of the curved wall and sleeve portions are bent radially outwardly to form the abutting fianges 50 and 50which are rigidly secured together. The attaching sleeve portionfiB isadapted to be attached to the exhaust pipe [3 in any suitable manner, asby being clamped thereon by the strap M and bolt H5, or by any othersuitable means, as more fully described above.

A plurality of gas diverting members 3!, 32 33 and 21 which correspondto like numbered members of the previously described construction, areprovided between the flanges 52, 53, of the casing iii, and all aresecured thereto-at their forward side edges by integral flanges 63, 64,and 65, 65 The rear gas diverting member 2'l' is secured to the rear capOr tail member 66. This cap member is in the form of a loop having itsend edges extending forwardly and telescoped within the rearwardlyextending flanges 6'5, 68, of the rear gas diverting member 21 The capmember has flanges 69 on its edges that are rigidly connected to theflanges 52 and 53 of the casing 5 l as by welding or the like.

The gas diverting members 3H, 32 33 and 21 are curved, as at 53%, withthe concave side forward, and have their outer edges curved rearwardlyfor directing the escaping gas rearwardly.

The front end plate or wall W has its inner or forward end connected tothe connector member 59, and the other gas diverting plates 3%, 32 33and 21* are arranged to extend progressively inwardly toward the axis ofthe channel a H, from front to rear, as indicated by the dotted linesmn, oi q-r and s-t, which indicate the planes of the inner edges ofthese members, as shown in Fig. 5 of the drawings. It will thus be seenthat the exhaust gases, or gases under pressure, flowing rearwar'dlythrough the channel 1!, will have a portion thereof diverted outwardlyby the plate 3N, and a further portion of the gas diverted laterallyoutwardly by the plate 32. Another portion of the remaining stream willbe diverted laterally by the plate 33 and still another portion will bediverted outwardly from the remaining gas stream by the plate 21 so thatonly a portion of the original stream will-pass the plate 2'! throughthe rear portion of the passage H. The rear portion of this passage isenlarged, as at 52, so that the gas in this portion of the stream isconsiderably expanded immediately prior to its discharge into theatmosphere.

The space between any two adjacent gas di verting plates may be termedexpansion chambers, and there are a plurality of gas expanding plateswithin each of these chambers. Since the gas diverting plates aresubstantially alike, only those between the plate or wall it and thefirst gas diverting plate 3 i need be described.

All of the gas expanding plates 35*, 38 37 38 3%, Mi and I have theirinner ends in the same planethat is, inclined toward the main passage lltoward the rear. These gas expanding plates or members are arranged intwo sets--the members of each set being substantially alike. Forinstance, the plates indicated by the odd numbers are alike, and thoseindicated by the even numbers are also alike.

All of these plates are slightly curved, with the concave faceforwardly, and are arranged closer together at their inner edge portionsthan at their outer so as to provide passages of gradually increasingcross-sectional area toward their outer ends so as to expand the gaspassing along the same. This is accomplished in the same manner asdescribed above. One way of securing this result is to describe thecurves as arcs of circles, with the centers of the circles outwardly ofthe casing in such'position that the inner edges of the plates are morenearly parallel with the center line of the unit, while the outer edgeportions of the plates are morenearly perpendicular thereto. Such anarrangement will result in laterally extending passages very much largerin cross-section at their outer ends than at their inner ones.

The-plates designated by the odd numbers, with letteredexponents,terminate short of the outer edge of the flanges 52, 53, while thoseplates designated by the even numbers, with lettered exponents, extendoutwardly to the outer edge of the flanges 52, 53, and are bent slightlyrearwardly so as to direct the escaping gas outwardlyand rearwardly.

The arrangement is the same as that already described, and shownin Fig.2, except that rectangular plates instead of circular plates areemployed for the gas or exhaust expanding memhere.

The outer ends of these expanding members are held in spaced relation bybolts 13, H (see Figs, 4 and 7) which pass through local bent portions15 formed in these plates. Suitable spacer sleeve members 18 areprovided between each two adjacent plates, as in the previouslydescribed construction.

In the operation of the device, the exhaust passing rearwardly throughthe exhaust pipe 13 into the silencer unit will have an outer portiondown to the dotted line m-n skimmed off or iverted into the expansionchamber it formed by the late 3H; and this portion of the exhaust willpass outwardly between the expanding plate:- Is 35 35 Lil' 33 39 th diand gas divertin plate 31*, and in doing so it will expand and dischargeoutwardly and rearwardly into the atmosphere at a greatly reducedpressure, as in the previous construction. The entire gas stream willbegin to expand as soon as the exhaust leaves the sleeve 58, and willcontinue to expand as it passes each expansion chamber in succession, asdescribed above. The remaining portion of the gas stream passing alongthe passage it, beyond the diverting disc, will expand in the nextchamber "Id and will have another portion diverted by the plate 32 andthis portion, represented by the space between the dotted lines m-n and0-l will pass into'the second expansion chamber 10, where the expansionprocess is repeated, and the trapped exhaust will pass out between theexpanding plates into the atmosphere in the manner just described.

Likewise, the remaining portion of the exhaust will expand as it passesthe expansion chamber lll and will have a part thereof diverted by theplate 33*, and this part, represented as the space between the lines o-pand q-r, will be trapped in the expansion chamber HP and pass outwardlybetween the expanding plates, as already described.

The same process will occur at the rear end of the unit, where the gasdiverting plate Zl' will divert a portion of the remaining stream, asrep resented by the dotted lines q-r and ir -t. This gas will bediverted into the expansion chamber 50 and pass outwardly between theplates therein, as described above.

The entire stream expands to a certain extent as it passes from onechamber to the other, so that the central stream, by the time it reachesthe rear end'of the silencer unit, has its velocity greatly reduced, andis further expanded and its velocity decreased still more in passingthrough the rear cap member 65, so that it is finally discharged, withlittle or no noise, into the atmosphere.

In both forms of construction high speed movement of the silencer unitthrough the air, with portions of the exhaust diverted laterally andrearwardly from the casing, tends to create a partial vacuum within therear cap member and in the rear of the unit, which will materiallyassist in scavenging the engine cylinders, thereby increasing the poweroutput of the engine. Even though the unit be motionless, the passage ofthe laterally and rearwardly discharged gas from the front portion ofthe unit across the lateral passages toward the rear will tend to createa partial vacuum in those passages, due to the principle of entrainmentof gases.

The number of diverting plates may each or both be increased ordecreased in either form of construction, as may be desired. While inthe constructions shown the diverting and expanding members are ofcertain forms, it is understood that the structures disclosed are by wayof example only and that other forms may be utilized so long as theyprovide means for expanding the gas or for reducin its velocity prior toits discharge into the atmosphere.

It will thus be seen that the main stream of exhaust gas is reduced involume and pressure at intervals as it moves toward the rear, and thatthe portions diverted from the main stream, as

well as the main stream itself, are expanded prior to their dischargeinto the atmosphere, so that the lateral discharges, as well as thegreatly reduced main discharge, will be expanded to such an extent thatthe pressure will not be much above that of the atmosphere, whereby theexhaust will be almost, if not entirely, noiseless.

It is thought from the foregoing, taken in connection with theaccompanying drawings, that the construction and operation of my devicewill be apparent to those skilled in the art, and that changes in size,shape, proportion or detail may be made without departing from thespirit and scope of the appended claims.

I claim as my invention:

1. In a muiller for releasing a compressed gaseous stream to theatmosphere, means providing channel for said stream, said channel beinopen to the atmospher along at least one side, and a plurality oftransverse plates dividing said open side of the channel into aplurality of lateral passages from said channel to the atmosphere. saidplates at their inner edges curving upstream to relatively acute anglesto the axis of said channel and overlapping at their inner ends torestrict the inner ends of said passages, said plates curving outward tosubstantially less acute angles to the axis of said channel therebyspreading apart to progressively increase the cross-sectional areas ofsaid lateral passages for substantial expansion of the gas therein priorto escape of the gas to the atmosphere.

2. In a muiller for releasing a compressed gaseous stream to theatmosphere, means providing a channel for said stream, said channelbeing open to the atmosphere along at least one side, and a plurality oftransverse plates dividing said open side of the channel into aplurality of lateral passages from said channel to the atmosphere, saidplates at their inner ends being inclined upstream at acute angles tothe axis of said channels and spreading apart at their outer ends, atleast some of said plates extending laterally beyond adjacent platesdownstream therefrom and being turned downstream at their outer ends todivert escaping gas across the edges of said adjacent plates.

3, In a mufller for releasing a compressed gaseous stream to theatmosphere, means providing a channel for said stream, said channelbeing open to the atmosphere along at least one side, and a plurality oftransverse plates dividing said open side of the channel into aplurality of lateral passages from said channel to the atmosphere, saidplates at their inner ends being inclined upstream, at least some ofsaid plates at their outer edges extending laterally beyond adjacentplates downstream therefrom and having said outer edges turned towardsaid adjacent plates to divert escaping gas across the edges of saidadjacent plates.

4. In a mufiler for releasing a compressed gaseous stream to theatmosphere, a plurality of transverse plates forming at least one sideof a channel for said stream, said plates having their inner edgesspaced along the periphery of said stream longitudinally of the streamto form lateral escape passages to the atmosphere, said plates at theirinner edges being inclined upstream at acute angles to the axis of thestream and spreading apart toward their outer edges for expansion of thelaterally escaping gas, and a plurality of orifice means spaced alongsaid channel in the zone of said plates dividing said channel into aseries of expansion chambers communicating with the atmosphere throughsaid escape passages, each of said expansion chambers being definedperipherally by the inner edges of a plurality of said transverseplates.

5. In a mufller, a construction as set forth in claim 4 in which saidorifice means are progressively restricted.

6. In a mufller for releasing a compressed gaseous stream to theatmosphere, means providing a channel for said stream, said channelbeing open to the atmosphere on at least one side and being open to theatmosphere at its end, said channel being unobstructed along its axis, aplurality of transverse plates along said open side of the channeldividing said open side into a plurality of closely spaced lateraldischarge passages, said plates at their inner edges curving upstream torelatively acute angles to the axis of said channel and overlapping attheir inner ends to restrict the inner ends of said passages, saidplates spreading apart toward their outer edges to permit expansion ofgas in said discharge passages.

7. In a mufiler for releasing a compressed gaseous stream to theatmosphere, means directing said stream along a discharge path openlaterally to the atmosphere, support means extending longitudinally ofsaid path spaced laterally from the axis of the path, a plurality oftransverse plates mounted on said support means adjacent said path, anda plurality of spacers mounted on said support means to hold said platesspaced apart to define a series of lateral discharge passages, the inneredges of said plates being directed upstream and positioned relativelyclose together, said plates spreading apart toward their outer edges topermit expansion of gas in said discharge passages.

8. In a mulller for releasing a compressed gaseous stream to theatmosphere, means directing said stream along a discharge path openlaterally to the atmosphere, support means extending longitudinally ofsaid path spaced laterally from the axis of the path, a plurality oftransverse plates mounted on said support means adjacent said path, anda plurality of spacers mounted on said support means to hold said platesspaced apart to define a series of lateral discharge-passages, the inneredges of'said plates being directed upstream and positioned relative- 13close together, said plates spreading apart toward their outer edges topermit expansion of gas in-said'discharge passages, some of said platesextending inward further than the majority of the plates therebydefining expansion chambers along said path.

9, Ina muffler for releasing a compressed gaseous stream to theatmosphere, means directing said stream along a discharge path openlaterallyto' the atmosphere, support means extending longitudinally ofsaid path spaced laterally from the axis of the path, a plurality oftransverse plates mounted on said support means adjacent saidpath, and aplurality of'spacers mounted on said support means to hold said platesspaced apart to define a series of lateral discharge passages, the inneredges of said'plates being directed upstream and positioned relativelyclose together, said plates spreading apart toward their outer edges topermit expansion of gas in said discharge passages, some of said platesextending inward further than the majority of the plates therebydefining expansion chambers along saidpath, the successive entrances tosaid chambers b'eing progressively restricted.

I. In-amufiler for releasing a compressed gaseous stream to theatmosphere, a series of expansion chambers having inlet and outletopenings along the axis ofsaid stream, each of said expansion chambershaving at least one side open to the'atmosphere and having a series oflateral wall members dividing said open side into a series of lateraldischarge passages, the inner edges of said well members being directedupstream.

H In a mufller for releasing a compressed gaseous stream totheatmosphere, a series of expansion chambers having inlet and outletopenings along the axis of said stream, the successive inlet openingsbeing progressively restricted, each of said expansion chambers havingat least one side open to the atmosphere: and having a series of lateralwall members dividing said open'side into a series of lateral discharge.passages, the inner edges of said wall members being directed upstream.

12. In a mufiler for releasing a compressed gaseous stream to theatmosphere, at seriesof expam sion chambers having inlet and outletopenings along theaxis of said stream, each of said expansion chambershaving at least one side open to the atmosphere and having a series oflateral wall members dividing'said open side into a series of lateraldischarge passages, the inner edges of said wall members being directedupstream, the outer edges of said wall members beingdirected downstreamwhereby the discharge from one passage tends to lower the pressure atthe outer end of the adjacent passage downstream therefrom.

13. In a muffieriorreleasing a compressed gaseousstream to theatmosphere, aseries ofexpansion chambers having inlet and outletopenings along the axis of said stream, each of said expansion chambershaving at least one side open to the atmosphere and having'a series oflateral Wall members dividing said open side into a series of lateraldischarge passages, the inner edges ofsaid wall members being directedupstream, the outer edges of some of said wall members extending outwardbeyond the outer edges of adjacent wall members downstream therefrom andbeing turned toward said adjacent wall members for diversion ofdischargegases toward'the adjacent wa11members.

14. In a muffler for releasing a compressed gaseous stream to theatmosphere, a casing forming a channel open along one side, transversediverting plates spaced along said open side of the casing for divertinggases from said channel, and transverse expanding plates positionedbetween said diverting plates to form escape passages in which thediverted gases are expanded and from which the expanded gases aredischarged into the atmosphere.

HERBERT L. MAGILL.

